Remove SPO Site Mailbox using CSOM, REST, anything

Question

How do I remove site mailbox not manually? What I have tried so far:

• Powershell remove-msoluser and remove-mailbox don't remove the app from SharePoint Online site. If you had a working mailbox and remove it with these cmdlets, you will start getting "Almost ready" and "Setting up" error messages after you click on the mailbox.
  

• I tried accessing $context.Web.AllProperties and modify/deleting/removing these properties:
  

  $webProps = $context.Web.AllProperties
  
  $webProps.Set_Item("ExchangeTeamMailboxSiteCollectionUrl", $NULL)
  
  $webProps["ExchangeTeamMailboxEmailAddress"]=$NULL
  
  $webProps.FieldValues.Remove("ExchangeTeamMailboxEmailAddress")
  
  $context.Web.Update()
  
  
  $context.ExecuteQuery()
  $context.Load($webProps)
  $context.ExecuteQuery()
  

None of the above had any effect and after the .ExecuteQuery() the properties are still there with the same values as before.

• The site mailbox is not a list and cannot be removed as such from ListCollection of the site.

Answer 1

If the goal only to remove Site Mailbox settings, then you could try the following example:

Function Remove-WebProperty([Microsoft.SharePoint.Client.Web]$Web,[string]$Name)
{
    $webProperties = $Web.AllProperties
    if ($webProperties.FieldValues.ContainsKey($Name) -eq $true) {
        $webProperties[$Name] = $null
    }       
}

$context = New-Object Microsoft.SharePoint.Client.ClientContext($Url)
$context.Credentials = Get-SPOCredentials -UserName $UserName -Password $Password

$context.Load($context.Web.AllProperties)
$context.ExecuteQuery()
$mailboxKeys = @("ExchangeTeamMailboxEmailAddress","ExchangeTeamMailboxSiteCollectionUrl","ExchangeTeamMailboxSiteID","ExchangeTeamMailboxSharePointUrl")
$mailboxKeys | ForEach-Object { Remove-WebProperty $context.Web $_ } 
$context.Web.Update()
$context.ExecuteQuery()

$context.Dispose()